1. Field
The present invention relates to a transmission device as well as an array antenna control method and device, which are preferably used in a base station etc. composing a wireless communication system.
2. Description of the Related Art
Related art examples [1]-[3] as described herebelow are known in the array antenna control art for a base station:
Related Art Example [1]: Not Shown
A base station in a wireless communication system transmits a common channel signal to be propagated to overall a cell (i.e. all users) by using a dedicated (exclusive use) non-directivity antenna.
On the other hand, individual channel signals for users following the above common channel signal are transmitted by using an array antenna after having adjusted the amplitude and the phase thereof so that each individual channel signal may have a desired directivity due to interferences among antenna elements composing the array antenna. This enables each individual channel signal to be propagated to each user without requiring a high transmission power.
However, due to requiring a dedicated non-directivity antenna for propagating the common channel signal, the setting space interferes with a miniaturization of the base station and increases development costs.
In order to address this, related art examples [2] and [3] as described herebelow have already been proposed:
Related Art Example [2]: Not Shown
A base station in a W-CDMA (Wideband Code Division Multiple Access) or TDMA (Time Division Multiple Access) wireless communication system performs a signal transmission by using one of antenna elements composing an array antenna when propagating the common channel signal (See, e.g. Japanese patent application publication No.2003-158479 or No. 2005-176160).
Related Art Example [3]: Not Shown
A base station in a W-CDMA wireless communication system provides the common channel signal to all antenna elements composing the array antenna to be transmitted (See, e.g. Japanese patent application publication Nos. 2006-5874 and 2003-60549).
The above related art examples [2] and [3] eliminate the use of the dedicated non-directivity antenna such as in the above related art example [1].
In the above related art example [2], one antenna element of the array antenna is employed to transmit the common channel signal, whereat a high transmission power of propagating the common channel signal to overall the cell is required, so that amplifiers or the like connected to the antenna elements should be of a high performance and a high output, increasing a power consumption and development costs of the entire base station.
Also, in the above related art example [3], the common channel signal of the same frequency is transmitted from each antenna element, thereby causing interferences where a null direction with no signals being propagated exists, so that the common channel signal is eventually transmitted with some directivity, failing to achieve non-directivity.